I have bitched about the implant thing ever since its existence was made aware to me. TCW '08 series is infamous for breaking previously established canon, contradicted tons of shit, and in general making stupid ideas. In the previously established lore the reason was that the Fett Clones were genetically altered so that they would be more loyal, follow orders better, and be less rogue like Fett was; that's what the Null ARC Troopers were, clones w/o the alterations making them more willing to accept orders, as they were of the first batch made.